A torque fluctuation absorbing apparatus is provided at an output shaft of an engine and/or an electric motor, for example, in a hybrid drive unit which includes the engine and the electric motor as a power source, and absorbs (restrains) fluctuation torque generated by the engine and the electric motor. A known torque fluctuation absorbing apparatus described in WO2006-079306A includes a second component member (i.e., indicated with reference number 3 in WO2006-079306A) having two surfaces (i.e., indicated with reference numbers 5, 6 in WO2006-079306A) which are provided having space from each other, and a first component member (i.e., indicated with reference number 2 in WO2006-079306A) and a third component member (i.e., indicated with reference number 8 in WO2006-079306A) are provided between the two surfaces. When the third component member (8) and the first component member (2) relatively move, a surface of the third component member (8) and a surface of the first component member (2) are configured to be pushed towards the respective surfaces (5, 6). The third component member (8) and the first component member (2) are provided with inclines (9, 10, 12, 13) so that the third component member (8) and the first component member (2) move relatively from each other having a predetermined play in a circumferential direction. The third component member (8) is arranged with no load applied in a radial direction and in an axial direction relative to the first component member (2) and the second component member (3).
In case level of inertia of the third component member (8) is small (e.g., when radius is small, or when large inertia is not achieved because of space), even when the third component member (8) is dragged by the first component member (2), adequate frictional torque may not be attained.
Further, because the third component member (8) moves freely in a radial direction and in an axial direction, rattling sound may be generated by a contact of the third component member to other components.
Further, because the third component member (8) moves in the axial direction, when the inclines of the first component member (2) and of the third component member (8) come in contact, instantaneously, the third component member (8) moves in a vertical direction relative to the inclines, which delays generations of the load in the axial direction, and thus hysteresis does not work quickly.
EP0529669B discloses a two-mass flywheel which generates hysteresis while constantly pressing a friction member by means of a coned disc spring. According to the constructions described in EP0529669B, the friction member extends in a radial direction, and protrusions which are in contact with a first component member (rivet) in predetermined intervals in a circumferential direction are provided. When the first component member and a second component member are twisted equal to or greater than a predetermined level of amplitude (i.e., rotational angle), upon a contact of the protrusions and the first component member, hysteresis starts being generated. With the foregoing structure in which hysteresis is varied based on changes of amplitude, when predetermined load of the coned disc spring is increased for the purpose of setting large degree of hysteresis properties by increasing frictional force, there is a possibility of generating big slapping sound by a contact of the friction member and the rivet when the hysteresis is generated. Further, when large degree of the hysteresis is set to be generated, because input of the torque fluctuation assumes relatively small, the friction member does not slide when the first component member and the second component member are twisted within slight amplitude, and thus vibrations at an engine side is not adequately absorbed.
A need thus exists for a torque fluctuation absorbing apparatus which is not susceptible to the drawback mentioned above.